Snowshovel
New member
Well the day started off perfect, we started up mountain and by the time we got to the trail head there was 10 inches of fresh powder on the trail and more falling in buckets. About 5 miles in I was in the lead and as we started to go up an incline i gave my (new to me, bought used last week) 03 Mountain Viper more gas. The result was bogging and the sled dying... hmm i thought bad gas from last year? fouled plugs? improper jetting as the altitude increased? So after inspecting the plugs the center one looked like it was burning lean, hardly wet at all after running for at least 45 minutes. Swapped in new plugs, and tried to start it, the crank would not turn, i pulled on the rope and she would come out about 5 inches and stop dead.
Fearing i had somehow seized the engine up I pulled the clutch shroud off and tried turning the primary by hand. At first it seemed stiff but then gave way and was turning fine. After many attemps the sled would not start so i hooked up my snatch strap and towed her out using my sons 600 Mountain Max. Once we got back to the trailer, i figured wtf lets give it another go before we try to drag the sled up the ramp into the trailer. Couple pulls and she fired right up, but something didnt sound right. It was almost like a piston was knocking, and the engine was shuddering.
I gave her some gas got it 1/2 way up the ramp and heard the sickening sound of the center piston rock going through the bottom of the case. A mad dash after moving everything off the floor to avoid the coolant that was leaking everywhere we popped the hood open to survey the damage. First thing out of my buddy's mouth "Rob we got debri" you dont want to know the first thing out of mine. The center piston rod had come loose and popped a hole right in the bottom of the case. I just bought this sled 8 days ago, the guy i bought it from said it was awesome for him and other than some minor "kissed a tree" repair he had no issues. It had 7000 miles on it and after looking it over had no visable defects other than a minor oil leak.
I had all fluids full, I was using oil the reservoir had gone down some from where we started. Only maintenance i have done on it was clean the power valves yesterday, which after pulling the top end off looked fine. So no way the powervalves caused this, di i just get the $hitty end of the stick and it was me the engine happened to fail on? Those of you who have owned these sleds please weight in and give your opinions. I am attaching photos of the damage, and am looking for a new motor if anyone has one.
Also is there a way to test your oil pump with the motor tore apart? A way to energize it and watch it pump to ensure it is working before i get a nerw motor and do it all over again?
Top end damage
looking in to the center piston
another of the center chamber
Fearing i had somehow seized the engine up I pulled the clutch shroud off and tried turning the primary by hand. At first it seemed stiff but then gave way and was turning fine. After many attemps the sled would not start so i hooked up my snatch strap and towed her out using my sons 600 Mountain Max. Once we got back to the trailer, i figured wtf lets give it another go before we try to drag the sled up the ramp into the trailer. Couple pulls and she fired right up, but something didnt sound right. It was almost like a piston was knocking, and the engine was shuddering.
I gave her some gas got it 1/2 way up the ramp and heard the sickening sound of the center piston rock going through the bottom of the case. A mad dash after moving everything off the floor to avoid the coolant that was leaking everywhere we popped the hood open to survey the damage. First thing out of my buddy's mouth "Rob we got debri" you dont want to know the first thing out of mine. The center piston rod had come loose and popped a hole right in the bottom of the case. I just bought this sled 8 days ago, the guy i bought it from said it was awesome for him and other than some minor "kissed a tree" repair he had no issues. It had 7000 miles on it and after looking it over had no visable defects other than a minor oil leak.
I had all fluids full, I was using oil the reservoir had gone down some from where we started. Only maintenance i have done on it was clean the power valves yesterday, which after pulling the top end off looked fine. So no way the powervalves caused this, di i just get the $hitty end of the stick and it was me the engine happened to fail on? Those of you who have owned these sleds please weight in and give your opinions. I am attaching photos of the damage, and am looking for a new motor if anyone has one.
Also is there a way to test your oil pump with the motor tore apart? A way to energize it and watch it pump to ensure it is working before i get a nerw motor and do it all over again?
Top end damage
looking in to the center piston
another of the center chamber
Snowshovel
New member
ttt please
dirtjumper895
New member
Looks like major detonation to me. Bad/old gas, too high of compression ect.... Detonation RUINS bearings. Did you run brand spanking new gas this trip?
Snowshovel
New member
It had an almost empty tank when i bought it maybe an inch worth of gas in it. I filled it up from the pump from there..
dirtjumper895
New member
From the looks of it, i do not think it was oil pump related. The pil pumps on these sleds are crazy good, i dont think ive ever read about one failing. I do however think that jetting and possibly bad gas were the major contributor.
hereismylife
Active member
I would love to see pics of the carbs. pilot,main bowl,main jet. Also I wonder what compression you have on the other 2 cilinders
Everything lines up with dirty carbs or clogged fuel system. If the bearing was already damaged, you shouldn't have gotten that far.
Did the gauge show any warning? I looks like she may have been hot. The underside of that piston will tell you a lot.
Be sure to find the root cause and correct it, or it will likely happen again to a rebuild motor.
Note for future reference: When a high performance 2-stroke is down on power, and especially after any type of seizure, do not try to start it until the root cause is determined and corrected. It can save lots of time and money. The fuel system carries the lubrication which is the lifeblood of the engine.
If you can post or link to better pictures, we can likely tell you what the debris is that is melted to the top of the piston. It may be pieces of rings, bearings, cases, or the piston itself.
When you clean the carbs, don't just blow them out. Try to find a blockage in the fuel circuits first, and then blow them clean. You want to be sure that you find the cause.
Did the gauge show any warning? I looks like she may have been hot. The underside of that piston will tell you a lot.
Be sure to find the root cause and correct it, or it will likely happen again to a rebuild motor.
Note for future reference: When a high performance 2-stroke is down on power, and especially after any type of seizure, do not try to start it until the root cause is determined and corrected. It can save lots of time and money. The fuel system carries the lubrication which is the lifeblood of the engine.
If you can post or link to better pictures, we can likely tell you what the debris is that is melted to the top of the piston. It may be pieces of rings, bearings, cases, or the piston itself.
When you clean the carbs, don't just blow them out. Try to find a blockage in the fuel circuits first, and then blow them clean. You want to be sure that you find the cause.
I think Dings post covers it all. Great response!
For interests sake:
I have seen that same type of piston/cylinder head damage on one of my old 540 VMAXs. I had seized a piston[too lean] I cleaned up the cylinder and just put a new piston/rings in...everything else looked good, so I jetted it up and went riding. After about 30min of use it seized again, because of the rod big bearing disintigration, the damage looked the same as yours. I learned right then + there : if you seize a cylinder due to being too lean, the heat has probably damaged the rod bearing as well so you better get the crank redone as well!
This may be what led to your issues.
JM.02c
For interests sake:
I have seen that same type of piston/cylinder head damage on one of my old 540 VMAXs. I had seized a piston[too lean] I cleaned up the cylinder and just put a new piston/rings in...everything else looked good, so I jetted it up and went riding. After about 30min of use it seized again, because of the rod big bearing disintigration, the damage looked the same as yours. I learned right then + there : if you seize a cylinder due to being too lean, the heat has probably damaged the rod bearing as well so you better get the crank redone as well!
This may be what led to your issues.
JM.02c
staggs65
Moderator
like ding said, you goota clean them carbs. every year!
i'm sure you wont make that mistake again
Not to throw another wench in this for you but... That is what my piston and head looked like when my conecting rod bearing let go last year in Muni. And it also sounds like similar circumstances. Since I was going up a hill let off then got on the gas and motor bogged and died.
Things I have learned since this has happened are that spark plugs make a huge impact on your motor. I blew mag side, but on that day i had my mbrp can on which moves my pipe closer to that cylinder making that cylinder hotter, which then means the BR9ES i was running was not cooling enough and was probily misfiring(predettonating the gas due to the grounding strap being hot) I have also been told since then that a vast majority of gas not has ethanol which burns hotter and easier. The solution for the ethanol from NGK is either run 1 plug cooler(BR10ES) with the gas 10thou less plug gap or run BR9EIX as the cutaway on the ground strap helps cool it faster and prevent detanation due to ethanol. The other main thing is majority of the viper crank failures are the middle cylinder(this on runs hotter as it gets no extra air cooling from the sides of the cylinder as they are too close to cylinder 1 and 3). The NGK rep recomended running a colder plug in the centre cylinder as it runs hotter by nature than the other 2. Seems to make sense to me.
The other thing is a majority of these crank failures have been since 2006 when ethanol was added to a majority of gas avaiable to the public. Does it need different oil? Oil companies will say yes. Others will say no. Does it need different plugs? Plug companies will say yes but the funny thing is the 500SS uses BR10EYS and has basically the same motor as the pre 2006 revs and they used BR9EYA's.....
All somthing to think about.
Things I have learned since this has happened are that spark plugs make a huge impact on your motor. I blew mag side, but on that day i had my mbrp can on which moves my pipe closer to that cylinder making that cylinder hotter, which then means the BR9ES i was running was not cooling enough and was probily misfiring(predettonating the gas due to the grounding strap being hot) I have also been told since then that a vast majority of gas not has ethanol which burns hotter and easier. The solution for the ethanol from NGK is either run 1 plug cooler(BR10ES) with the gas 10thou less plug gap or run BR9EIX as the cutaway on the ground strap helps cool it faster and prevent detanation due to ethanol. The other main thing is majority of the viper crank failures are the middle cylinder(this on runs hotter as it gets no extra air cooling from the sides of the cylinder as they are too close to cylinder 1 and 3). The NGK rep recomended running a colder plug in the centre cylinder as it runs hotter by nature than the other 2. Seems to make sense to me.
The other thing is a majority of these crank failures have been since 2006 when ethanol was added to a majority of gas avaiable to the public. Does it need different oil? Oil companies will say yes. Others will say no. Does it need different plugs? Plug companies will say yes but the funny thing is the 500SS uses BR10EYS and has basically the same motor as the pre 2006 revs and they used BR9EYA's.....
All somthing to think about.
Mac
Member
sideshowBob - I'm not agreeing with a bad crank just because it seized on top end. Obviously you had a case where the crank went bad after the rebuild. The crank won't turn normally because your dragging that bad piston. I have seized 5 pistons top end without touching the crank at 9400 miles. The top end rebuilds on these motors is easy and can be completed quickly. Inspect that rod bearing and look for discoloration and freeplay. Pulling the crank is a lot more involved and time consuming and expensive. I would rebuild the top end and only do the crank if it seizes and is required. I agree with Ding dirty carbs. I would bet the pilot jet is clogged. I think we are in for a long season of this type of seizure due to bad fuel and dirty carbs.
Mac said:
I do agree if it is a light seizure the crank probably will be OK, but if it has been lean + hot it is going to damage the rod bearings. I to have had light seizures and not done the crank but if you have holed or erroded a piston and the rod shows any discolouration at all you are better off doing the the crank as well as it will save a lot more parts + $$$
Snowshovel
New member
Alot of good info here and I will take it all into consideration, I havent tore into the carbs yet just removed them as a unit and set them in a bucket to drip. If it is jetting how would i know? The previous owner installed Boysen reeds in the carbs supposedly and put a Hartman clutch on it. Shouldnt he have rejetted it when he did those 2 mods? I will probably start inspecting the carbs and taking pictures over the next few days, ill snag some copper safety wire from work to see if there is a blockage.
Anyone recommend a reputable place to start looking for a rebuilt motor? And also do i need a puller to get the Primary clutch off? I removed the long center bolt but it wont budge.
Oops forgot to answer one of the other question, No I had no pre warning and no warning lights illuminated.
Anyone recommend a reputable place to start looking for a rebuilt motor? And also do i need a puller to get the Primary clutch off? I removed the long center bolt but it wont budge.
Oops forgot to answer one of the other question, No I had no pre warning and no warning lights illuminated.
Mac
Member
No Jetting change required for those mods. Yes clutch puller required. Pull the float bowl off the carb on the bad cylinder. The pilot jet is inside a tube that hangs down from the carb. You will need a skinny small screwdriver to remove this jet. Dont blow any air until you inspect this jet. Hold it up to the light and see if you can see light through this jet. Also check the main jet for a clog. Careful with the wire idea. Air or brake cleaner or carb cleaner should do. Also check the other carbs. Did you take notice that the airbox that is was installed properly. An air leak will lean out the engine. Check the rubber boot for a tear. If the previous owner installed reeds make sure the gaskets look ok. Remember the previous owner could have made an install mistake. Verify that the mains and pilots were not changed. Check the needles too. When my sled hit 8500 miles my needle clip sawed through the aluminum needle. The needle dropped down to block all fuel in the main jet and POW.... lost cylinder.
9801srx
Member
was this the first time the sled was rode after summer storage? if it threw the rod out through the base you deffinently lost the lower rod brg which will destroy the top of the piston and head like that. you can't tell if that damage is deto or not if it passed a rod brg through there.if that carb checks out and there was no air leaks or signs of deto on the other two cyl's i would suspect poor summer storage. also check to see if the ring land between the two rings is broken away from the piston , that usually happens because of deto before a rod brg goes because of it.
Snowshovel
New member
Mac,
I have new to snowmobile engines and carbs, would i be able to see the things you are talking about, needles etc... with a novice eye?
9801 I dont think i will be able to tell if the rings on the bad piston came apart as that piston is seized up in the cylinder tighter than a drum.
I have new to snowmobile engines and carbs, would i be able to see the things you are talking about, needles etc... with a novice eye?
9801 I dont think i will be able to tell if the rings on the bad piston came apart as that piston is seized up in the cylinder tighter than a drum.
Snowshovel
New member
More carnage pics
racerrob6m
New member
Boy...I recognise those pics of the piston. Had the same thing 2yrs ago with a Phazer II motor on my wifes sled. And, we traced it back to "bad gas" sitting too long, ie, the "fine ethanol" gas here in OR which has the 6-8 week shelf life. LESSON LEARNED there!! 
One rod bearing got some rust, & 1st ride 5 miles out, it started to come apart. Fortunatley, she was not at WOT when she noticed the "noise", & shut it down. We did not attempt to start it after it turned over a bit stiffer than normal & then towed it out. So, in my case, we just lost the crank & left piston & rod.
I now run only non ethanol fuel...no problems since then & no jetting changes
either.
Good luck with your new "fixing project"!
One rod bearing got some rust, & 1st ride 5 miles out, it started to come apart. Fortunatley, she was not at WOT when she noticed the "noise", & shut it down. We did not attempt to start it after it turned over a bit stiffer than normal & then towed it out. So, in my case, we just lost the crank & left piston & rod.
I now run only non ethanol fuel...no problems since then & no jetting changes
either.
Good luck with your new "fixing project"!
Wow! That broken rod is a sad sight! I am amazed how dry it looks around the rod's "Exit Wound"!